iOS 当我尝试关闭模态时崩溃

Question

我使用模态转换动画对控制器进行模态化。但是当我试图关闭控制器时，程序崩溃了。 Xcode 没有记录任何消息。

我的过渡动画有问题。当我删除转换代码时，它运行良好。

所以我的代码有什么问题？

- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext {
    _transitionContext = transitionContext;
    UIView *toView = [transitionContext viewForKey:UITransitionContextToViewKey];
    UIView *fromView = [transitionContext viewForKey:UITransitionContextFromViewKey];
    CALayer *toVcLayer = [CALayer layer];
    toVcLayer.frame = toView.layer.frame;
    [toVcLayer addSublayer:toView.layer];

    _transformLayer = [CATransformLayer layer];
    _transformLayer.frame = [UIScreen mainScreen].bounds;
    [_transformLayer addSublayer:fromView.layer];
    CATransform3D ct = CATransform3DIdentity;
    ct = CATransform3DMakeTranslation(0.0, 0.0, -1.0);
    ct = CATransform3DRotate(ct, M_PI, 0.0, 1.0, 0.0);
    toVcLayer.transform = ct;
    [_transformLayer addSublayer:toVcLayer];

    CATransform3D at = CATransform3DIdentity;
    at = CATransform3DRotate(at, M_PI, 0.0, 1.0, 0.0);
    CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"transform"];
    animation.toValue = [NSValue valueWithCATransform3D:at];
    animation.duration = 1.0;
    animation.delegate = self;
    [_transformLayer addAnimation:animation forKey:nil];

    [transitionContext.containerView.layer addSublayer:_transformLayer];
}

- (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag {
    [_transitionContext.containerView addSubview:[_transitionContext viewForKey:UITransitionContextToViewKey]];
    [_transitionContext completeTransition:YES];
}

Answer 1

问题可能在于在其他层之间移动层。您正在尝试插入已经在其他地方有超层的层。我不知道为什么它在呈现时还没有崩溃，但它在关闭时崩溃也就不足为奇了。

关闭视图控制器时，它们的状态不同。主要是，toView 已经是 containerView 的子视图。毕竟是 fromView 展示的时候。使用您的代码 view/layer 层次结构变得非常混乱，最终导致崩溃。

解决方法很简单。而不是创建单独的 transformLayer 来保存其他图层并对其进行动画处理。分别为每一层制作动画。示例：

-(void)animateTransition(id<UIViewControllerContextTransitioning>)transitionContext {
    _transitionContext = transitionContext;
    UIView *toView = [transitionContext viewForKey:UITransitionContextToViewKey];
    UIView *fromView = [transitionContext viewForKey:UITransitionContextFromViewKey];

    if (toView.superview == nil)
        [transitionContext.containerView addSubview:toView];

    const NSTimeInterval duration = 1.0;
    const CGFloat translationX = 400.0;

    toView.layer.transform = CATransform3DMakeTranslation(translationX, 0.0, 0.0);

    CABasicAnimation *toAnimation = [CABasicAnimation animationWithKeyPath:@"transform"];
    toAnimation.toValue = [NSValue valueWithCATransform3D:CATransform3DIdentity];
    toAnimation.duration = duration;
    toAnimation.delegate = self;

    CABasicAnimation *fromAnimation = [CABasicAnimation animationWithKeyPath:@"transform"];
    fromAnimation.toValue = [NSValue valueWithCATransform3D:CATransform3DMakeTranslation(-translationX, 0.0, 0.0];
    fromAnimation.duration = duration;

    [fromView addAnimation:fromAnimation forKey:nil];
    [toView addAnimation:toAnimation forKey:nil];
}

-(void)animationDidStop:(CAAnimation*)anim finished:(BOOL)flag {
    [_transitionContext completeTransition:YES];
}

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